Graveyard of the Fallen: Hidden Cinematic:
When you have won ALL of the fights at each of the heads on pikes, return to the first burning head on a pike which is near the start of the level. If you interact with it you will enter a new area and trigger a hidden cinematic when you move Aarbron forward.

Unlock Credits Mini-Game:
When you complete ALL the levels under the same difficulty setting with a total rank of at least 'Silver' a mini-game will start during the credits. In this mini-game you must estroy the airships to unlock special game art and two secret enemies. Defeating both of these enemies will add them to your bestiary. If you destroy ALL the airships and defeat the bosses you will earn a trophy. You can retry this mini-game whenever you desirea by viewing the credits again from the 'Map' menu.

Unlock Aarbron Punching Mini-Game:
You can unlock this feature during the loading screen by pressing X(2), Square, Triangle.